One such prior art gate comprises various essential items in common with a gate of the present invention for the case where the level-regulated reach is the downstream reach. These essential items in common are initially described in order to specify the technical context in which the present invention is situated. The comprise:
a channel along which the upstream and downstream reaches follow one another in a longitudinal horizontal direction;
a horizontal oscillation axis disposed transversely across the downstream end of the channel; and
an oscillating assembly, said assembly moving about said axis between angular positions extending between a closed position and an open position, with each position being defined by an opening angle relative to said closed position, said assembly itself comprising:
a frame having an upstream branch and a downstream branch respectively upstream and downstream from said axis;
a plate carried by said upstream branch and disposed in said channel to close it to a greater or lesser extent, thereby controlling the water flow rate through the gate, said channel being closed in said closed position and open in said open position, said plate being cylindrical in shape about said axis to ensure that the hydrostatic thrust it receives from the upstream reach does not apply any interfering couple to said oscillating assembly;
a float carried by said downstream branch so as to dip a variable portion of its height into the water of said downstream reach in order to apply a float couple directed towards said closed position and increasing firstly with an increase in said downstream level and secondly with an increase in said opening angle, said float being substantially in the form of a body of revolution about said axis and occupying a limited angular sector in such a manner that said float couple varies substantially linearly with said angle; and
balancing masses situated at least in part at a longitudinal distance from said axis in order to apply a gravity couple to said oscillating assembly and directed towards said open position.
The purpose of these masses is to achieve balance in the assembly when the level of the downstream reach is at a reference level. The masses are situated at least in part at a vertical distance above said axis so that said balance is a substantially neutral balance which occurs at least approximately in all of said angular positions. The substantially neutral nature of this balance has the major advantage that any difference between the downstream level and the reference level imposes a sufficiently large angular displacement on the oscillating assembly to eliminate said difference in level quickly and almost completely.
Such gates are described in French Pat. Nos. 2 071 299 and 2 076 249, and in corresponding U.S. Pat. Nos. 3,683,630 and 3,643,443.
More particularly, the float of such a prior gate is fixed at the downstream end of the frame. Part of it dips into a tank which communicates with the downstream reach via a slot formed in the bottom thereof. A first gate balancing mass is inserted into the float via a hatch situated in the top thereof. A second balancing mass is inserted into a bin fixed on the frame at a point situated substantially vertically above the oscillation axis when the gate is in its closed position. These masses are chosen in such a manner as to ensure that the gate is balanced regardless of its opening angle when the water level in the downstream reach is at the same level as the oscillation axis. Under these conditions, the gate tends to close when the downstream level exceeds the axis level and to open when the downstream level drops below the axis level. The gate thus automatically regulates the downstream level to a reference level constituted by the level of the oscillation axis.
Such a gate serves to regulate the level of a canal or basin very reliably and accurately without requiring any energy to be supplied thereto. However, it is designed for reference levels that do not vary since it is not possible in practice to raise or lower the oscillation axis. In some circumstances, it is desirable to be able to vary the reference level.
Various dispositions have been proposed in other situations for varying the reference level, and these are described in U.S. Pat. No. 4,027,486 and European patent application number 0 083 800.
These dispositions include, in particular, means for varying a volume of water contained in a float carried by the upstream face of the plate in order to regulate the upstream level. It would not be economically feasible to implement these dispositions in the above-described constant downstream level gate since the float of such a gate is large and would require very large volumes of water to be inserted or removed. As described in French Pat. No. 2 071 299, the inside volume of the float is used as a bin for ballast and insufficient volume is available for water transfers.
In addition, these dispositions do not allow the substantially neutral nature of the balance of the oscillating assembly to be conserved.
The object of the present invention is to provide a sluice gate for automatically regulating a level which is simple to implement and for which the reference level may be adjusted either manually by easy local action or else remotely by transmitting a low power signal, in particular by means of a telephone line or a radio link, while nevertheless retaining the advantages of an oscillating assembly in which balance is substantially neutral.